1. Field of the Invention
The present invention relates generally to various apparatus for remotely releasing tethered assemblies of fiber optic cable assemblies, and more specifically, to various apparatus for remotely releasing tethers and tethered assemblies interconnected at Flexible Network Access Points (“FlexNAP” or “FNAPP”) along a distribution cable in order to access the tethers and tethered assemblies at a vault, hand hole, man hole, other structure or remote location within an optical network.
2. Technical Background
In “Fiber-to-the-Premises” (FTTP) and other optical networks, referred to generically herein as “FTTx” networks, pre-engineered fiber optic distribution cables including FlexNAPs are being developed and deployed to facilitate the delivery of services to subscribers over a plug-and-play network. The most recently developed FlexNAP systems typically include distribution cables having pre-selected optical fibers terminated, also referred to herein as “pre-terminated”, and accessed from the distribution cable at an access point, and routed separately away from the distribution cable to provide branches, referred to herein as “tap points,” “mid-span access locations,” “branch points” or “tether attach points.” At these tap points, the pre-selected and pre-terminated optical fibers of the distribution cable are often spliced or otherwise optically connected to a length of optical cable referred to herein as a “tether.” The tether may terminate in a connection terminal, or may be used to provide optical fiber to an optical connection terminal, network interface device or other optical network terminal located within reach of the tether. The tether may also be used for mitigating span length measurement issues resulting from errors in pre-engineered cable assembly installations. The tether is typically lashed to the distribution cable during assembly and installation and released as needed.
Several methods for FlexNAP system deployment currently exist including, but not limited to, aerial drive-off, aerial pull-through, buried trench and buried duct installations. While early generations of closures were relatively large in diameter and inflexible to installation requirements, later and present generation closures include flexible overmolded solutions on the order of only about a few inches in both diameter and length, thus facilitating installation in both aerial and buried environments. With regard to buried installations in particular, installation within these environments is typically difficult because of diameter constraints and having to work within a closed environment. Installation is especially difficult through about 1.25 inch diameter ducts, a common diameter requirement of telecommunications service providers.
Current FlexNAP systems typically include one or more tethers having lengths ranging from about a few feet to several hundred feet in length. In small diameter buried duct environments, the tether typically terminates in a low-profile tethered assembly including at least one connector, for example a multi-fiber (Con2r-MT) connector available from Corning Cable Systems of Hickory, N.C. During installation within a buried duct environment, it is often necessary to access the tethered assembly at a vault, hand hole, man hole or other buried structure, commonly referred to herein as a “hand hole”, to connect the multi-fiber ferrule with another predetermined connector. Based on the number of tethered assemblies, varying tether lengths, locations of buried hand holes, the manner in which the FlexNAP system was installed and the engineering of the system itself, it is very difficult to ensure that each tethered assembly will be properly positioned and accessible at its predetermined hand hole. Most often, the distribution cable and only a portion of the tether length are visible at the hand hole, not the tethered assembly itself. Therefore, it is often necessary to detach or “unlash” the tether and tethered assembly from the distribution cable in order to pull the tether and tethered assembly back into the hand hole for access.
In aerial installation environments, the detachment of the tether may be as simple a process as going to each lashing location (where tape or tie-wraps are most commonly used) and removing or cutting each lashing along the length of the tether. In buried duct environments, this method of detaching the tether is much more difficult because of the lack of access to the lashings. Although it may be possible for an installation crew to manually remove the lashings by purposely overshooting each hand hole and then while pulling back to the proper position, remove the lashings as the distribution cable returns into the hand hole, this would be very manually labor intensive and require multiple operators working together from adjacent hand holes. Thus, what is needed is a way of releasing lashed tethers and tethered assemblies after cable assembly installation in order to allow the tethers and assemblies to be pulled into a hand hole or other buried structure for access. In particular, what is needed are remote tether release apparatus positioned along a cable along the length of the tether. Further, what is desired are remote tether release apparatus that allow a sufficient length of a tether to be released from the distribution cable from a hand hole at any point along the tether length, thus providing a cable assembly with a built-in feature for compensating for tap point placement errors that occur during system installation.